Tests not only measure the contents of memory, they can also enhance learning and long-term retention. We report two experiments inspired by Tulving's (1967) pioneering work on the effects of testing on multitrial free recall. Subjects learned lists of words across multiple study and test trials and took a final recall test 1 week after learning. In Experiment 1, repeated testing during learning enhanced retention relative to repeated studying, although alternating study and test trials produced the best retention. In Experiment 2, recalled items were dropped from further studying or further testing to investigate how different types of practice affect retention. Repeated study of previously recalled items did not benefit retention relative to dropping those items from further study. However, repeated recall of previously recalled items enhanced retention by more than 100% relative to dropping those items from further testing. Repeated retrieval of information is the key to long-term retention.